A skill useless from the beginning, <Restoration>. Regardless, in order to save a childhood friend who sacrificed her body to protect him, Touru spent twenty-five years developing the skill. Once completed, the skill could completely defy the world’s common sense. Touru, the girl, the naughty child they picked up in a back alley, and the old landlord lady join together as companions, setting out on an adventure to become heroes. A man who lived through the depths of despair decided to move forward and widen his horizons.

Impression
This has recently started getting a manga adaptation, only 2 chapters seems to be out in the wild right now. Protagonist has restoration skill that he can use to restore any object to pristine state. He grinds for 25 years in order to fully develop his skill, at which point, it begin to affect living objects. Using that skill he "heals" his childhood friend who's time was frozen with another skill after she suffered fatal injury. The protagonist start living together with his newly recovered childhood friend. The other adventurers seems to look down on protagonist for not having a decent combat skill. At a glance, it looks like a standard fantasy, but might be a good idea to keep an eye on it for the future.

@myskaros They're childhood friends from the same village. She was seriously wounded in a monster outbreak and someone with a skill to stop time (I think her father?) stopped her time to be able to find a cure. Said cure took 25 years (for the MC to level up his skill), which is why there's the age gap.